The disclosure relates to an internal combustion engine having an intake system for feeding in charge air, an exhaust-gas discharge system for discharging exhaust gas, and at least one combined exhaust-gas aftertreatment system, which is arranged in the exhaust-gas discharge system and has an intake housing for feeding in exhaust gas.
Within the context of the present disclosure, the expression internal combustion engine comprises diesel engines and spark-ignition engines, but also hybrid internal combustion engines, which use a hybrid combustion process, and hybrid drives, which comprise not only the internal combustion engine but also an electric machine which can be connected in terms of drive to the internal combustion engine and which receives power from the internal combustion engine or which, as a switchable auxiliary drive, additionally outputs power.
According to prior art, to reduce pollutant emissions, internal combustion engines are equipped with various exhaust gas aftertreatment systems. Even without additional measures, oxidation of the unburned hydrocarbons and of carbon monoxide duly takes place in the exhaust-gas discharge system at a sufficiently high temperature level and in the presence of sufficiently large oxygen quantities. However, on account of the exhaust gas temperature which falls quickly in the downstream direction, and the consequently rapidly decreasing rate of reaction, said reactions may be quickly halted. A possible lack of oxygen may be compensated by blowing in secondary air. However, special reactors and/or filters may need to be provided in the exhaust gas discharge system in order to noticeably reduce the pollutant emissions under all operating conditions.
Thermal reactors try to ensure a temperature level that is as high as possible by minimizing the heat losses by means of heat insulation, a sufficiently large reactor volume being intended to ensure a long dwell time of the exhaust gases. Both the long dwell time and the high temperature level assist the desired re-oxidation. The poor efficiency with sub stoichiometric combustion and the high costs may be disadvantageous. For diesel engines, thermal reactors are not effective on account of the temperature level always being lower than desired.
For the stated reasons, according to prior art, in spark-ignition engines use is made of catalytic reactors, which by using catalytic materials increase the rate of certain reactions and ensure an oxidation even at low temperatures. If nitrogen oxides are additionally to be reduced, this may be achieved by the use of a three-way catalytic converter, which however for this purpose requires stoichiometric operation (air fuel ratio λ≈1) of the spark-ignition engine within narrow limits. Here, the nitrogen oxides are reduced by means of the non-oxidized exhaust-gas components which are present, specifically the carbon monoxides, and the unburned hydrocarbons, wherein said exhaust-gas components are oxidized at the same time.
In internal combustion engines which are operated with an excess of air, that is to say for example spark-ignition engines operating in the lean-burn mode, but in particular direct-injection diesel engines or else direct-injection spark-ignition engines, the nitrogen oxides contained in the exhaust gas cannot be reduced in principle, owing to the lack of reducing agent. For the oxidation of the unburned hydrocarbons and of carbon monoxide, an oxidation catalytic converter is therefore provided in the exhaust-gas discharge system. To realize an adequate conversion, a certain operating temperature is required. The so-called light-off temperature may be 120° C. to 250° C.
To reduce the nitrogen oxides, use is made of selective catalytic converters (SCR) catalytic converters, wherein reducing agent is purposely introduced into the exhaust gas in order to selectively reduce the nitrogen oxides. As reducing agent, in addition to ammonia and urea, use may also be made of unburned hydrocarbons. The latter is also referred to as HC-enrichment. The unburned hydrocarbons may be introduced directly into the exhaust-gas discharge system or else may be fed in by means of engine-internal measures, specifically by means of a post-injection of additional fuel into the combustion chamber after the actual combustion. Here, the post-injected fuel should not be ignited in the combustion chamber by the main combustion that is still taking place or by the high combustion gas temperatures that exist even after the end of the main combustion, but rather should be introduced into the exhaust-gas discharge system during the charge exchange.
It is also possible to reduce the nitrogen oxide emissions by means of nitrogen oxide storage catalytic converters (LNT). Herein, the nitrogen oxides are initially (during a lean-burn mode of the internal combustion engine) absorbed, that is to say collected and stored, in the catalytic converter before being reduced during a regeneration phase, for example by means of sub stoichiometric operation (λ<1) of the internal combustion engine with a lack of oxygen.
Further possible engine-internal measures for realizing rich, that is to say sub stoichiometric, operation of the internal combustion engine are exhaust-gas recirculation and, in the case of diesel engines, throttling in the intake system. It is possible to dispense with engine-internal measures if the reducing agent is introduced directly into the exhaust-gas discharge system, for example by injection of additional fuel. During the regeneration phase, the nitrogen oxides are released and converted substantially into nitrogen dioxide, carbon dioxide, and water. The frequency of the regeneration phases is determined by the overall emission of nitrogen oxides and the storage capacity of the LNT.
The temperature of the storage catalytic converter should preferably lie in a temperature window between 200° C. and 450° C., such that firstly a rapid reduction of the nitrogen oxides is ensured and secondly no desorption without conversion of the re-released nitrogen oxides takes place, such as may be triggered by excessively high temperatures.
The sulfur contained in the exhaust gas is likewise absorbed in the LNT and is regularly removed in the course of desulfurization. For this purpose, the LNT may be heated to high temperatures, usually of between 600° C. and 700° C., and supplied with a reducing agent, which in turn can be attained by the transition to rich operation of the internal combustion engine. The higher the temperature of the LNT, the more effectively the desulfurization proceeds, though an admissible maximum temperature must not be exceeded.
According to prior art, to minimize the emission of soot particles use is made of regenerative particle filters, which filter the soot particles out of the exhaust gas and store them. The accumulated soot particles may be burned off intermittently during the course of the regeneration of the filter. The high temperatures for the regeneration of the particle filter, of approximately 550° C. without catalytic assistance, may be reached during high engine loads and high engine speeds operations. It is therefore important to implement additional measures to ensure a regeneration of the filter under all operating conditions.
Since both the exhaust gases of spark-ignition engines and also the exhaust gases of diesel engines contain unburned hydrocarbons, carbon monoxide, nitrogen oxides and also soot particles (in different quantities and qualities), use is often made of combined exhaust-gas aftertreatment systems, which comprise one or more of the above-described catalytic converters, reactors and/or filters.
A combined exhaust-gas aftertreatment system may for example comprise a storage catalytic converter and a particle filter. The particle filter as a honeycomb filter then serves at the same time as a carrier substrate for forming the storage catalytic converter. Herein, the honeycomb filter is coated with a catalytic material that is suitable for storing and reducing the nitrogen oxides contained in the exhaust gas. Such a system is characterized by a compact design. Furthermore, a plurality of carrier substrates may be reduced since the carrier substrate of the particle filter is used at the same time to form the storage catalytic converter.
It is attempted to arrange exhaust-gas aftertreatment systems as close as possible to the outlet of the internal combustion engine, such as close to the outlet openings of the cylinders, in order to be able to make optimum use of the hot exhaust gas and ensure a rapid light-off of the exhaust-gas aftertreatment systems and a sufficiently high system temperature. The path of the hot exhaust gases to the various exhaust-gas aftertreatment systems should be as short as possible, such that the exhaust gases are given little time to cool down and the exhaust-gas aftertreatment systems reach their operating temperature or light-off temperature as quickly as possible, in particular after a cold-start of the internal combustion engine.
It is therefore always sought to minimize the thermal inertia of the part of the exhaust-gas discharge system between the outlet opening at the cylinder and the exhaust-gas aftertreatment system, which can be achieved by reducing the mass and the length of said part.
For the reasons stated above, the exhaust manifold is frequently integrated into the cylinder head. The integration of the exhaust manifold additionally permits dense packaging of the drive unit. Furthermore, the exhaust manifold can benefit from a liquid-type cooling arrangement that may be provided in the cylinder head, such that the manifold does not need to be manufactured from expensive materials that can be subject to high thermal load.
Further measures are required to realize the temperatures necessary for an efficient exhaust-gas aftertreatment reliably and according to requirements, for example after a cold-start. Also, further measures are required to ensure or promote dense packaging of the exhaust-gas discharge system together with the exhaust-gas aftertreatment system, and consequently of the entire drive unit.
The inventors herein have recognized the above issues and identified an approach by which the issues described above may be at least partly addressed. In one example, a method comprises: during cold start conditions, closing a plurality of vanes coupled to an exhaust turbine outlet cone to concentrate exhaust flowing towards a portion of an exhaust aftertreatment device, and after attainment of exhaust aftertreatment device light-off temperature, adjusting an orientation of the plurality of vanes to introduce turbulence and homogeneity to exhaust flow reaching the exhaust aftertreatment device.
The object of the present disclosure is to provide an internal combustion engine in which the high temperatures required for an efficient exhaust-gas aftertreatment can be realized more quickly, in particular after a cold-start, and which has a dense packaging of the exhaust-gas discharge system together with the exhaust-gas aftertreatment.
Said object is achieved by means of an internal combustion engine comprising an intake system for feeding in charge air, an exhaust-gas discharge system for discharging exhaust gas, and at least one combined exhaust-gas aftertreatment system, which is arranged in the exhaust-gas discharge system and has an intake housing for feeding in exhaust gas. The housing comprises an adjustable ring-shaped guide device that leaves an opening free in the middle and comprises guide vanes that can be rotated by means of an adjusting device arranged in the intake housing. Each of the guide vanes is arranged on a guide vane specific shaft. A wall may be involved in forming the intake housing and bounding it on the outside enclosing the ring-shaped guide device while forming a gap between the guide vanes and the wall in the manner of a frame. In a closing position, the adjustable ring-shaped guide device may cover an annular segment of a deployable inlet flow cross section in the manner of a shutter.
In the case of the internal combustion engine according to the disclosure, the at least one exhaust-gas aftertreatment system is equipped with an adjustable ring-shaped guide device, which is arranged in the intake housing of the exhaust-gas aftertreatment and with which the exhaust-gas flow can be influenced in various ways before entering the exhaust-gas aftertreatment system.
For example, turbulences, such as vortexes, can be introduced into the exhaust-gas flow by means of the guide device. The exhaust-gas flow may also be deflected, in particular widened. This allows a uniform flow through the exhaust-gas aftertreatment system and its carrier substrate to be realized or ensured. While according to prior art the flow rate may vary more locally, such as not every region of the carrier substrate is flowed through by the same amount of exhaust gas, according to the disclosure, the exhaust gas to be after-treated is distributed uniformly or more uniformly over the entire exhaust-gas aftertreatment system. The local flow rates are equalized or evened out, for which reason the amounts of exhaust gas flowing through the exhaust-gas aftertreatment system do not vary locally as much or at all. The effects described above have a number of advantages at the same time.
On the one hand, the intake housing, which regularly widens in the direction of the exhaust-gas aftertreatment system, can be made comparatively short, and the exhaust-gas aftertreatment system can be advantageously arranged close to the engine.
On the other hand, the exhaust-gas aftertreatment system that is present is used in its entirety, and consequently more effectively, and it is not the case that some regions, in particular centrally arranged regions, are used more intensively than other regions, for example outer peripheral regions. To this extent, the exhaust-gas aftertreatment system as such can be made more compact, such as with a smaller volume, whereby the costs for the exhaust-gas aftertreatment system may also be reduced.
The provision according to the disclosure of a guide device consequently allows a dense packaging of the exhaust-gas discharge system together with the exhaust-gas aftertreatment system, and consequently a dense packaging of the drive unit as a whole.
In addition, the ring-shaped guide device can be adjusted and transferred into a closing position, in which the guide vanes of the guide device cover an annular segment of the flow cross section in the inlet region of the exhaust-gas aftertreatment in the manner of a shutter.
Then an opening through which the entire exhaust gas is conducted remains centrally in the closed position of the guide device. Transferring the guide device into the closed position has the effect of constricting the exhaust-gas flow and concentrating the entire exhaust gas flow to be after-treated to a locally confined region of the exhaust gas aftertreatment system. Such a concentration of the exhaust gas flow proves to be advantageous to maintain the temperature of the exhaust-gas aftertreatment system even with small amounts of exhaust gas. In particular, the local heating up of the exhaust-gas aftertreatment system after a cold-start may be brought about by enforced constriction or concentration of the exhaust-gas flow.
The internal combustion engine according to the disclosure is an internal combustion engine in which the high temperatures required for an efficient exhaust gas aftertreatment can be realized more quickly, in particular after a cold-start, and which has a dense packaging of the exhaust-gas discharge system together with the exhaust gas aftertreatment.
According to the disclosure, the guide device may have multiple rotatable guide vanes. The adjusting device may have a rotatable adjusting ring, wherein the guide vanes are adjustable by means of turning the adjusting ring.
The adjusting device has a rotatable adjusting ring, which is preferably mounted coaxially in relation to the intake housing. The guide vanes are kinematically coupled to the adjusting ring via intermediate elements, such that the guide vanes can be adjusted by turning of the ring. Pivotable levers may be provided as intermediate elements for the kinematic coupling of the adjusting ring to the guide vane specific shafts.
The levers may be respectively connected at their one end, on the shaft side, in a rotationally conjoint manner to a guide vane specific shaft and are mounted at their other end, on the ring side, movably in a recess of the adjusting ring, such that the guide vanes are adjustable by means of turning the adjusting ring. The levers may be directed inwardly from the adjusting ring, the adjusting ring is with respect to the levers an outer adjusting ring, which leads to a greater diameter of the adjusting ring. The pivotable levers may, however, also be directed outwardly from the adjusting ring. In an alternate embodiment, the adjusting ring then forms with respect to the levers an inner adjusting ring, which is characterized by a comparatively small diameter. In comparison with an outer adjusting ring, an inner adjusting ring leads to a more compact exhaust-gas aftertreatment system.
At least one turbine may be arranged in the exhaust-gas discharge system, preferably upstream of the at least one exhaust gas aftertreatment system. It may be advantageous to be able to use the enthalpy of the hot exhaust gases optimally and ensure a rapid response behavior of the turbine. At least one turbine may be a turbine of an exhaust-gas turbocharger which comprises a turbine arranged in the exhaust-gas discharge system and a compressor arranged in the intake system are advantageous.
Supercharging is primarily a method for increasing performance in which the air required for the combustion process in the engine is compressed, as a result of which a greater air mass can be fed to each cylinder in each working cycle. In this way, the fuel mass and therefore the mean pressure can be increased. For supercharging, use is preferably made of an exhaust-gas turbocharger, in which a compressor and a turbine are arranged on the same shaft. The hot exhaust-gas flow is fed to the turbine which expands in the turbine with a release of energy, as a result of which the shaft is set in rotation. The energy supplied by the exhaust-gas flow to the turbine and ultimately to the shaft is used for driving the compressor which is likewise arranged on the shaft. The compressor supplies and compresses the charge air fed to it, as a result of which supercharging of the cylinders is obtained. A charge-air cooler is advantageously provided in the intake system downstream of the compressor, by means of which charge-air cooler the compressed charge air is cooled before it enters the at least one cylinder. The cooler lowers the temperature and thereby increases the density of the charge air, such that the cooler also contributes to improved charging of the cylinders, that is to say to a greater air mass. In this way, compression by cooling takes place.
The advantage of an exhaust-gas turbocharger in comparison with a mechanical charger is that no mechanical connection for transmitting power exists or is required between the charger and the internal combustion engine. While a mechanical charger extracts the energy required for driving it entirely from the internal combustion engine, it thereby reduces the output power and consequently adversely affects the efficiency, the exhaust-gas turbocharger utilizes the exhaust-gas energy of the hot exhaust gases.
Supercharging is a suitable means for increasing the power of an internal combustion engine while maintaining an unchanged swept volume, or for reducing the swept volume while maintaining the same power. In any case, supercharging leads to an increase in volumetric power output and an improved power-to-weight ratio. If the swept volume is reduced, it is thus possible to shift the load collective toward higher loads, at which the specific fuel consumption is lower. By means of supercharging in combination with suitable transmission configurations, it is also possible to realize so-called downspeeding, with which it is likewise possible to achieve a lower specific fuel consumption.
Supercharging consequently assists in the constant efforts in the development of internal combustion engines to minimize fuel consumption that is to say to improve the efficiency of the internal combustion engine.
It is a further basic aim to reduce pollutant emissions. Supercharging can likewise be expedient in solving this issue. With targeted configuration of the supercharging, it is possible specifically to obtain advantages with regard to efficiency and with regard to exhaust-gas emissions.
The torque characteristic of a supercharged internal combustion engine may be improved by using multiple turbochargers, for example by multiple turbines of relatively small turbine cross section arranged in parallel (in a way similar to a sequential supercharging arrangement), wherein, with increasing exhaust-gas flow rate, turbines are activated successively. The torque characteristic of a supercharged internal combustion engine may also be improved by means of multiple series-connected exhaust-gas turbochargers, of which one exhaust-gas turbocharger serves as a high-pressure stage and one exhaust-gas turbocharger serves as a low-pressure stage.
Embodiments of an internal combustion engine in which at least two exhaust-gas turbochargers are provided, each comprising a turbine arranged in the exhaust-gas discharge system and a compressor arranged in the intake system, may therefore also be advantageous for the reasons stated above.
Embodiments of the internal combustion engine in which the intake housing is widened in the direction of flow to the at least one exhaust-gas aftertreatment system may be advantageous. This assists a widening of the exhaust-gas flow in the inlet region of the exhaust-gas aftertreatment system and is conducive to uniform impingement of the entire exhaust-gas aftertreatment system with exhaust gas
Embodiments of the internal combustion engine in which the intake housing is of a funnel-shaped form may be advantageous in this connection. A funnel shape provides a continuous widening of the intake housing and a continuous widening of the exhaust gas flow with as little pressure loss as possible in the exhaust-gas flow. Also, the intake housing may be of frustoconical form.
A sleeve arranged in the intake housing may be provided. The sleeve maybe aligned coaxially in relation to the intake housing and may pass through the central opening in the ring-shaped guide device. The sleeve may be widened in the direction of flow toward the at least one exhaust gas aftertreatment system. The sleeve may be one of a conical form or a frustoconical form. In addition, a holding device may be provided for the sleeve.
Each guide vane specific shaft may be of rectilinear form. A rectilinear form of the shaft simplifies the kinematics of the adjusting device in such a way that the turning of the guide vane specific shaft at the end on the adjusting ring side brings about a purely rotational movement of the associated guide vane, whereas a cranked shaft would cause a tumbling movement of the guide vane, which makes it more difficult for the rotatable guide vanes to be arranged in the intake housing with almost no gap and makes it difficult for the guide vanes to be arranged in multiple different turning positions with almost no gap.
In the present case, the vanes perform a purely rotational movement when the ring turns. As a result, an almost gapless arrangement of the rotatable guide vanes in the intake housing is possible, specifically in every turning position of the vanes. The latter is a significant advantage in comparison with cranked shafts, since it is intended that the exhaust-gas flow should be conducted across the guide vanes, and not via a gap past the guide vanes.
An actuating device may be used for the turning of the adjusting ring, wherein the actuating device may be both an electrical actuating device and a mechanical actuating device. A mounting may be provided for the adjusting ring, for example in the form of a rolling bearing.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.